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GABA systemZopiclone
Zopiclone is a synthetic hypnotic of the cyclopyrrolone class. It acts at the same receptor site as benzodiazepines despite being structurally unrelated, and is the parent compound of eszopiclone (Lunesta). It amplifies GABA — the brain's primary calming signal — producing rapid, heavy sedation.
Zopiclone is a synthetic hypnotic of the cyclopyrrolone class. It is structurally unrelated to benzodiazepines but acts at the same receptor site, with broader subtype engagement.[1] Zopiclone is a positive allosteric modulator of GABA-A receptors, producing its effects by amplifying the brain's primary inhibitory signaling system.
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GABA systemDeveloped by Rhône-Poulenc in the early 1970s, zopiclone was patented in 1972 as the first of its chemical class.[1] It was approved in France in 1986 and became a standard prescription sleeping pill across Europe, Canada, and Australia. In the United States, only its isolated active form — eszopiclone (Lunesta) — received approval.[2]
Subjective effects include heavy drowsiness, muscle relaxation, anxiety relief, and memory gaps for events after dosing. The experience is defined by a rapid, weighted descent into sleep and a persistent bitter-metallic taste beginning within minutes — unique among sedatives.[3] Unwanted effects include next-day cognitive slowing,[4] complex sleep behaviors such as sleepwalking, and rebound effect insomnia when stopping.
Zopiclone produces physical dependence with regular use, though its dependence potential is lower than benzodiazepines;[1] deaths from zopiclone alone are rare.[5] The primary danger is combination: adding alcohol, opioids, or benzodiazepines transforms a manageable single-drug overdose into a potentially fatal one.[5] Four decades of clinical use provide a solid evidence base, though the effects of continuous use beyond 17 weeks remain unstudied.
History[edit]
Discovery
Zopiclone was synthesized by Rhône-Poulenc in the early 1970s as part of a program to develop sleeping pills structurally distinct from benzodiazepines.[1] It was patented in 1972 as the first of its chemical class — a scaffold unrelated to barbiturates, benzodiazepines, or imidazopyridines. First human studies, published in 1982–1983,[6][7] established its core absorption and elimination parameters.
Clinical adoption
France approved zopiclone in 1986, with Canada, Australia, the United Kingdom, and continental Europe following.[1] It was marketed as superior to benzodiazepines for preserving deep sleep with less next-day grogginess. Sepracor later isolated its active form — eszopiclone — which the US FDA approved in December 2004 as the first hypnotic approved without a time limit on use.[2]
Scheduling
The US Drug Enforcement Administration placed zopiclone in Schedule IV in April 2005.[8] In the United Kingdom it is classified under Schedule 4, Part I of the Misuse of Drugs Act 1971; Canada lists it under Schedule IV of the Controlled Drugs and Substances Act. New Zealand reclassified it as a Class C5 controlled drug in 2022.citation needed
The name zopiclone follows pharmaceutical naming conventions for the cyclopyrrolone class. Marketed as Imovane across Europe and Canada and as Zimovane in the United Kingdom, it is informally grouped with zolpidem and zaleplon as "Z-drugs" — non-benzodiazepine hypnotics that share the GABA-A benzodiazepine binding site despite complete structural divergence.
Chemistry[edit]
Structural class
Zopiclone is the prototypical cyclopyrrolone — a chemical family structurally unrelated to benzodiazepines, barbiturates, or zolpidem's imidazopyridine class.[1] Its molecular formula is C₁₇H₁₇ClN₆O₃ (molecular weight 388.8 g/mol). The primary site the body breaks it down is a carboxylate ester linkage that the liver cleaves as the dominant metabolic route, accounting for more than half the administered dose.[7]
Stereochemistry
Zopiclone exists as a racemic mixture — two mirror-image forms in equal proportion.[9] Only the S-(+)-enantiomer produces the hypnotic effect; the R-(-)-enantiomer is inactive. The isolated active form is marketed separately as eszopiclone (Lunesta).
Pharmacology[edit]
Mechanism of action
Zopiclone amplifies GABA — the brain's primary calming signal — by binding at the benzodiazepine site on GABA-A receptors.[1] It does not activate the receptor directly; it makes the brain's own GABA more effective, increasing the frequency of inhibitory signaling. Unlike zolpidem, zopiclone engages multiple receptor subtypes, which explains its combined sedative, anxiolytic, and muscle-relaxing effects.[10][11]
Pharmacokinetics
Zopiclone is rapidly absorbed after oral dosing, reaching peak blood levels within 30–60 minutes.[9] Oral bioavailability is approximately 77%, with about 20–25% lost to first-pass liver metabolism.[12] The liver processes it primarily through the enzyme CYP3A4,[13][14] and less than 7% exits unchanged in urine.[7] The characteristic bitter taste appears in saliva around 24 minutes after dosing,[3] and the compound passes into breast milk at concentrations approaching those in blood.[7]
Neuroscience[edit]
Where it acts
Zopiclone promotes sleep by suppressing the brain's wake-promoting centers — neurons that use histamine, norepinephrine, and serotonin to keep the body alert — while allowing sleep-promoting neurons in the hypothalamus to take over.[1][11] This produces a relatively fast shift from wakefulness into sleep, with better preservation of deep sleep than most benzodiazepines.
Residual impairment — slowed reactions, memory gaps, impaired driving performance — persists well beyond subjective sedation, lasting up to 10 hours after a standard dose.[4][15] A person may feel alert and functional while meaningfully impaired.
Why it matters
The memory-impairing effects arise from disruption of memory encoding in the hippocampus — the brain region that converts experiences into lasting memories.[5] GABA amplification blocks the synaptic changes this process depends on. This explains both the therapeutic forgetting of pre-sleep anxiety and the concerning amnesia for activities performed during incomplete arousal.
Several fundamental questions remain unanswered. Why does zopiclone preserve deep sleep while benzodiazepines suppress it, given both act at the same site? Structural studies reveal different binding modes,[16] but no functional explanation has been demonstrated.
Subjective Effects[edit]
Zopiclone's defining quality is speed and weight. The transition from wakefulness into drowsiness is abrupt — heavier and more immediate than the gradual sedation of benzodiazepines — and accompanied from the first minutes by a bitter-metallic taste that persists through the night. At therapeutic doses, the experience is simply: sleep.
Compared to zolpidem, zopiclone produces longer-lasting next-day impairment and a stronger amnestic component. Relative to benzodiazepine hypnotics, it preserves deep sleep more effectively while carrying a comparable combination risk profile.
Developed by Rhône-Poulenc in the early 1970s as the first cyclopyrrolone hypnotic, zopiclone was patented in 1972 and approved in France in 1986.[2] The compound was placed in Schedule IV of the US Controlled Substances Act in 2005, though racemic mixture zopiclone was never marketed there — only its active enantiomer eszopiclone (Lunesta) received FDA approval.[3][4] It is prescribed across Canada, Australia, and much of Europe under the brand names Imovane and Zimovane.
Subjective effects include sedation, anxiolysis, muscle relaxation, and anterograde amnesia. The experience is defined by a rapid, heavy drowsiness accompanied by a persistent bitter-metallic taste detectable within minutes of dosing[5] — a signature unique to the cyclopyrrolone class. Residual next-day cognitive impairment,[6] complex sleep behaviors, and rebound effect insomnia upon discontinuation are characteristic unsought effects.
Zopiclone produces physical dependence with prolonged use, though its dependence potential is consistently characterized as lower than that of benzodiazepines;[2] deaths from zopiclone alone are rare, with fatality predominantly tied to polydrug overdose.[7] The primary risk is combinatorial: concurrent CNS depressants — alcohol, opioids, benzodiazepines — transform a relatively forgiving single-agent overdose profile into a potentially lethal one. Four decades of clinical use provide a solid evidence base, though effects of continuous administration beyond 17 weeks remain unstudied.
History[edit]
Discovery
Zopiclone was synthesized by Rhône-Poulenc S.A. (now part of Sanofi) in the early 1970s as part of a program to develop hypnotics structurally distinct from benzodiazepines.[2] The compound was patented in 1972 as the first member of the cyclopyrrolone class — a novel scaffold bearing no structural relationship to barbiturates, benzodiazepines, or imidazopyridines. First human pharmacokinetic studies were published in 1982–1983,[8][9] establishing the core absorption and elimination parameters that guided clinical development.
Clinical adoption
Zopiclone received its first regulatory approval in France in 1986, with authorization following in Canada, Australia, the United Kingdom, and continental Europe.[2] It was marketed as a sleeping pill with meaningful advantages over benzodiazepines: better preservation of deep sleep and less next-day sedation. The compound's commercial significance expanded when Sepracor isolated its active S-(+)-enantiomer, eszopiclone, which the US FDA approved in December 2004 as the first hypnotic without a limitation on duration of use.[3]
Scheduling
The US Drug Enforcement Administration placed zopiclone into Schedule IV of the Controlled Substances Act in April 2005, citing dependence potential comparable to benzodiazepines.[4] In the United Kingdom it is classified under Schedule 4, Part I of the Misuse of Drugs Act 1971; Canada lists it under Schedule IV of the Controlled Drugs and Substances Act. New Zealand reclassified zopiclone as a Class C5 controlled drug in 2022 in response to growing misuse concerns.citation needed
The name zopiclone follows pharmaceutical conventions for the cyclopyrrolone class. Marketed as Imovane across most of Europe and Canada and as Zimovane in the United Kingdom, it is commonly grouped with zolpidem and zaleplon under the informal label "Z-drugs" — non-benzodiazepine hypnotics sharing the GABA-A benzodiazepine binding site despite complete structural divergence.
Chemistry[edit]
Structural class
Zopiclone is the prototypical cyclopyrrolone — a heterocyclic scaffold structurally unrelated to benzodiazepines, barbiturates, or the imidazopyridine class that includes zolpidem.[2] The core structure is a fused pyrrolo[3,4-b]pyrazine ring system with a 5-oxo group, representing a novel chemical approach to GABA-A modulation. That a completely different molecular scaffold could produce equivalent pharmacological effects at the benzodiazepine binding site was a significant finding, demonstrating that structural diversity at this target was achievable.
A 5-chloropyridinyl group at C-6 and a 4-methylpiperazine-1-carboxylate ester at C-7 complete the molecule. The carboxylate linkage is metabolically labile, providing the primary site for breakdown in the liver — the dominant metabolic route, accounting for over half the administered dose.[9]
Molecular properties
| Molecular formula | C₁₇H₁₇ClN₆O₃ |
| Molecular weight | 388.8 g/mol |
Stereochemistry
Zopiclone has a single chirality center and is sold as a racemic mixture of two mirror-image forms.[10] Only the S-(+)-enantiomer is pharmacologically active at GABA-A receptors; the R-(-)-enantiomer contributes nothing to the hypnotic effect.
The isolated S-(+)-enantiomer is marketed separately as eszopiclone (Lunesta). The two enantiomers also differ pharmacokinetically: the active S-form reaches higher blood concentrations, is cleared more slowly, and has a longer half-life than the inactive R-form.
Pharmacology[edit]
Mechanism of action
Zopiclone is a positive allosteric modulator of GABA-A receptors, binding at the benzodiazepine site located at the interface between the α and γ₂ subunits.[2] It does not activate the receptor directly; instead, it amplifies the effect of the brain's own GABA by increasing the frequency of chloride channel opening, strengthening inhibitory signaling. This mechanism is functionally identical to that of benzodiazepines despite complete structural divergence.
Unlike zolpidem, which is highly selective for α1-containing receptors, racemic mixture zopiclone engages α1-, α2-, and α3-containing receptor subtypes without strong preference.[1][11] This broader engagement likely accounts for zopiclone's combined sedative, anxiolytic, and muscle relaxant properties.[2]
The compound also inhibits nicotinic acetylcholine and NMDA receptors at high concentrations in laboratory settings,[1] but whether these secondary actions contribute to effects at normal therapeutic doses is unknown.
Structural analysis of eszopiclone at the benzodiazepine binding pocket revealed a binding mode dependent on specific hydrogen bonds — mechanistically distinct from zolpidem, which relies primarily on shape-based fitting within the pocket.[12] This difference may explain the two drugs' divergent effects on sleep architecture.
Pharmacokinetics
Zopiclone is rapidly absorbed after oral administration, reaching peak blood concentrations within 30–60 minutes.[10] Oral bioavailability is approximately 77%, with about 20–25% of the dose lost to first-pass liver metabolism.[13]
The liver breaks down zopiclone through three main routes: decarboxylation (accounting for over half the dose, producing CO₂ exhaled through the lungs), N-demethylation (yielding an inactive metabolite), and N-oxidation (producing an active metabolite).[10][9] CYP3A4 is the principal liver enzyme involved,[14][15] making zopiclone susceptible to drug interactions with CYP3A4 inhibitors and inducers.
Less than 7% of the dose is excreted unchanged in urine.[9] The compound enters saliva, producing the characteristic bitter taste at approximately 24 minutes post-dose,[5] and is excreted in breast milk at concentrations approaching those in blood.[9]
Neuroscience[edit]
Where it acts
Zopiclone's sedative and sleep-promoting effects arise from potentiating GABAergic inhibition across cortical and subcortical regions. The drug suppresses wake-promoting nuclei — histaminergic, noradrenergic, and serotonergic centers — allowing sleep-active neurons in the ventrolateral preoptic area to dominate.[2][11] The result is a relatively rapid transition from wakefulness into sleep, with preservation of slow-wave (deep) sleep that distinguishes zopiclone from most benzodiazepines.
Residual impairment — psychomotor slowing, impaired driving performance, and memory gaps — persists well beyond the period of subjective sedation, lasting up to 10 hours after a standard dose.[6][16] This disconnect between plasma clearance and functional recovery suggests downstream effects on neural circuits that outlast the drug's presence in blood.
Why it matters
Zopiclone's action is understood within the flip-flop switch model of sleep-wake regulation: mutual inhibition between wake-promoting and sleep-promoting neurons creates a bistable system, and GABA-A potentiation tips the switch toward sleep. The amnestic effects involve disruption of memory encoding in hippocampal circuits, where GABA-A potentiation impairs the synaptic strengthening that underlies new memory formation.[7]
This same mechanism explains both the therapeutic forgetting of pre-sleep wakefulness and the concerning amnesia for activities performed during incomplete arousal states.
Several fundamental questions remain unanswered. Why does zopiclone preserve deep sleep while benzodiazepines suppress it, given both act at the same receptor site? Structural studies reveal different binding modes,[12] but no functional explanation has been demonstrated.
Subjective Effects[edit]
Zopiclone's experiential signature is a swift descent into heavy drowsiness — more abrupt than the gradual anxiolytic warmth of benzodiazepine sedation, and accompanied from the outset by a pervasive bitter-metallic taste that no other sedative-hypnotic produces. At therapeutic doses the experience is simply sleepiness; at supratherapeutic doses, amnesia, behavioral disinhibition, and fragmented awareness emerge, shifting the character toward a deliriant-like state with impaired reality testing.
Compared to zolpidem, zopiclone produces longer-lasting next-day impairment and a more pronounced amnestic component. Relative to benzodiazepine hypnotics, it preserves slow-wave sleep more effectively but carries comparable abuse liability with extended use.
Effect Grid
Reliable sleep induction at 5–7.5 mg oral — the standard therapeutic range. Full hypnotic effect with preserved slow-wave sleep architecture. Sedation is pronounced and rapid, with most users falling asleep within 30 minutes. The bitter-metallic taste is universal. Thought deceleration and analysis suppression are moderate. Anterograde amnesia is possible at the upper end of this range.
Physical effects include moderate muscle relaxation, motor control impairment sufficient to affect balance and coordination, and mild dizziness. Respiratory effects are negligible at this dose in healthy individuals.
Residual psychomotor impairment is documented up to 10 hours post-dose at 7.5 mg. Do not drive or operate machinery for at least 8–10 hours after dosing, even if subjective drowsiness has resolved.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Vestibular distortion · Dreaming enhancement · Visual haze / noise · Auditory distortion · Visual morphing · Visual processing suppression · Auditory hallucinations · External hallucinations · Internal hallucinations
Visual morphing · Visual processing suppression · Auditory hallucinations · External hallucinations · Internal hallucinations
Dizziness · Insomnia · Dry mouth · Body high · Headache · Nausea · Brain zaps · Nystagmus (eye wobbles) · Trembling · Vomiting · Tactile hallucination
Headache · Nausea · Brain zaps · Nystagmus (eye wobbles) · Trembling · Vomiting · Tactile hallucination
Cognitive fatigue · Information processing suppression · Memory suppression · Thought deceleration · Memory fragmentation · Motivation suppression · Confusion · Language suppression · Thought disorganization · Compulsive redosing urge · Delusions of sobriety · Amnesia · Delirium · Delusions
Thought deceleration · Memory fragmentation · Motivation suppression · Confusion · Language suppression · Thought disorganization · Delusions of sobriety · Amnesia · Delirium · Delusions
Euphoria · Irritability
Craving · Depersonalization · Derealization · Sociability enhancement
Timeline
Bitter-metallic taste appears first, typically within 24 minutes. Drowsiness builds rapidly as plasma concentrations rise toward Tmax.
Full sedation and sleep induction. Slow-wave sleep architecture preserved. Maximum amnesia risk.
Sedation wanes as plasma levels fall below the effective threshold. Subjective drowsiness diminishes but cognitive slowing persists.
Residual psychomotor impairment, cognitive slowing, and potential morning grogginess without subjective sedation. Measurable performance deficits persist.
⚠ Do not drive or operate machinery for at least 8–10 hours after taking zopiclone 7.
Safety[edit]
- Acute toxicity
- Low
- Chronic toxicity
- Moderate
- Withdrawal
- Moderate
- Tolerance buildup
- slow
- Tolerance reset
- 10.5 days
- Physical
- Moderate
- Psychological
- Moderate
- Compulsive redosing
- Low
- Dose escalation
- Low
- Cross-tol.
- benzodiazepines · zolpidem · zaleplon
Toxicity
Acute toxicity
Deaths from zopiclone alone are rare.[5] Single-drug overdose typically produces deep sedation or coma, with respiratory depression uncommon in isolation. The benzodiazepine-site reversal drug flumazenil can reverse zopiclone-induced sedation.[5]
Fatality risk rises sharply with polydrug overdose. Post-mortem data include fatalities with zopiclone at toxic blood levels alongside other substances,[17][18] and European surveillance data found zopiclone most frequently involved in overdose events among the three Z-drugs.[19]
Respiratory effects
At the standard 7.5 mg dose, zopiclone does not worsen breathing during sleep in published studies.[20][21] Data in patients with chronic lung disease or sleep apnea are limited.
Liver effects
No significant liver toxicity has been reported at therapeutic doses. Pre-existing liver impairment substantially increases drug exposure because zopiclone is processed primarily by the liver.[12]
Psychological risks
Zopiclone can cause memory gaps for events after dosing, complex sleep behaviors — driving, eating, or walking during partial arousal with no memory afterward — visual hallucinations, and behavioral disinhibition.[5][22] Complex sleep behaviors are elevated by concurrent sedating medications and pre-existing sleep disorders.[23][24]
Irritability, emotional lability, and paradoxical agitation have been reported, with higher incidence in elderly patients.[5][25] Epidemiological data associate long-term hypnotic use with increased depression and mortality risk, though whether this is causal remains unestablished.[26]
Tolerance and dependence
Tolerance to the sleep-promoting effects develops more slowly than for benzodiazepines. A 17-week sleep laboratory study showed sustained efficacy without measurable tolerance,[27] and eszopiclone data extend to 12 months.[2] Cross-tolerance with benzodiazepines is expected given the shared binding site.[1][11]
Physical and psychological dependence develop with prolonged use. Dependence risk is equivalent to zolpidem[19] and is consistently characterized as lower than benzodiazepines but clinically significant — particularly in people with a history of substance use disorder.[1][14] Stopping after chronic use brings rebound effect insomnia, anxiety, disturbed dreams, and nausea;[2] gradual dose tapering is recommended.[28]
Drug Interactions
Zopiclone is processed by the liver enzyme CYP3A4. Drugs that block this enzyme raise zopiclone blood levels and intensify sedation: erythromycin,[9][13][14] azole antifungals (ketoconazole, itraconazole), clarithromycin, ritonavir, and cimetidine[29][14] all require caution, as does grapefruit juice.[29] Drugs that activate CYP3A4 — rifampicin[14] and carbamazepine[9][13] — reduce zopiclone levels and effectiveness.
Alcohol does not meaningfully alter how zopiclone is metabolized, but the combined sedation is dangerous.[30][14] All CNS depressants — opioids, benzodiazepines, sedating antihistamines, sedating antidepressants — carry the same additive risk.[29][14][5] Polydrug overdose with CNS depressants is the principal context for fatality.[5]
Contraindications
9 known- Concurrent CNS depressant use — Additive sedation and respiratory depression with alcohol,[30][14] opioids, benzodiazepines, and other sedating agents substantially increases overdose risk.
- Breastfeeding — Zopiclone is excreted in breast milk at concentrations approaching those in blood.[7]
- Severe liver impairment — bioavailability rises to approximately 97% and half-life extends to approximately 8.4 hours; mandatory dose reduction to 3.5 mg.[12]
- Elderly patients (over 70) — Bioavailability increases up to approximately 168% and half-life extends to approximately 8.1 hours; dose reduction to 3.75 mg required, with elevated falls risk and cognitive vulnerability.[12][31][32]
- History of substance use disorder — Elevated dependence risk.[19][33]
- Breathing difficulties — Caution warranted given the mechanism; zopiclone-specific data in chronic lung disease populations are limited.safety citation needed
- Driving and machinery — Avoid for at least 8–10 hours after a 7.5 mg dose; documented residual impairment persists up to 10 hours.[4][5]
- Pregnancy — Safety has not been established; fetal exposure is presumed given breast milk excretion data.safety citation needed
Harm Reduction[edit]
Forms & Identification
Zopiclone circulates almost exclusively as commercially manufactured pharmaceutical tablets, making identification more straightforward than for powders or liquids. Counterfeit tablets exist, particularly in jurisdictions where zopiclone is not locally manufactured. Visual inspection for consistent imprinting, correct tablet shape, and intact packaging provides a baseline check.
Because zopiclone produces a distinctive bitter-metallic taste within minutes of ingestion, absence of this taste from a purported zopiclone tablet is a meaningful warning sign.
Guidelines
- Take zopiclone only when able to commit to a full night of sleep (7–8 hours minimum)
- Take the tablet immediately before getting into bed — not hours beforehand
- Do not exceed the prescribed dose (7.5 mg standard adult; 3.75 mg for elderly or liver-impaired patients)
- Do not crush, split, or dissolve tablets
- Avoid alcohol entirely on days zopiclone is taken
- Keep car keys out of reach before dosing if complex sleep behaviors are a concern
- Limit use to the shortest effective duration — daily use beyond 2–4 weeks increases dependence risk
- Do not stop abruptly after more than a few weeks of daily use — taper gradually under medical guidance
Set & Setting
Zopiclone is designed to induce sleep and should be taken only in a safe sleeping environment with no need to drive, operate machinery, or make decisions for at least 10 hours. The bedroom should be prepared before dosing — once the drug takes effect, coordination and judgment deteriorate rapidly.
Individuals with a history of sleepwalking or complex sleep behaviors should inform a household member they have taken the medication.
Aftercare & integration. Next-day effects are common and expected. Residual cognitive impairment, slowed reaction time, and a persistent bitter taste may last up to 10 hours after a 7.5 mg dose. Do not drive or operate machinery during this period. Hydration and a normal meal help clear the lingering taste and support recovery.
If complex sleep behaviors occurred — evidence of eating, walking, or other activity with no memory — document what happened and consult a prescriber. This is a recognized adverse effect and may warrant discontinuation or dose adjustment.
Recovery & Support
Zopiclone dependence develops with regular use. The earliest sign is often difficulty sleeping without the medication — this rebound effect insomnia can feel like the original problem returning, making it harder to recognize as withdrawal. If daily use has extended beyond a few weeks, do not stop abruptly: taper gradually under medical supervision.
Cognitive behavioral therapy for insomnia (CBT-I) is the gold-standard alternative, with benefits that persist after treatment ends — unlike zopiclone, whose effects cease when the drug is stopped. Individuals struggling with zopiclone dependence can seek support through a prescribing physician, addiction services, or peer support organizations.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: Shallow or stopped breathing, blue-tinged lips or fingertips, inability to be roused by loud voice or sternal rub, or seizure activity all require immediate emergency response. Deep sleep alone is expected — unresponsiveness combined with abnormal breathing is the critical distinction.
- 1. Call emergency services immediately if breathing is slow, irregular, or absent
- 2. Place the person in the recovery position (on their side, airway clear) if unconscious but breathing
- 3. Do not induce vomiting
- 4. Do not leave the person alone
- 5. Monitor breathing continuously until help arrives
What to tell the dispatcher: Name the substance (zopiclone), approximate amount taken, time of ingestion, any other substances involved (especially alcohol, opioids, or benzodiazepines), and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
Reversal agent: Flumazenil can reverse zopiclone-induced sedation in a medical setting. It is not available over the counter and is administered only by medical professionals.
Legal Status[edit]
Zopiclone is a controlled substance in all major jurisdictions, classified alongside benzodiazepines and other sedative-hypnotics.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Schedule IV (Controlled Substances Act) | Final rule effective April 4, 2005.[8] Not commercially marketed; only eszopiclone (Lunesta) available. |
| United Kingdom | Schedule 4, Part I (Misuse of Drugs Act 1971) | Prescription-only medicine. Marketed as Zimovane. |
| Canada | Schedule IV (CDSA) | Available by prescription; generics widely available. |
| Australia | Schedule 4 (prescription only) | Distributed by Sanofi-Aventis as Imovane.citation needed |
| New Zealand | Class C5 (Misuse of Drugs Act) | Reclassified from prescription-only to controlled drug in 2022.citation needed |
| European Union | Prescription only (national regulations vary) | Widely available across EU member states. |
Legal status varies by jurisdiction and changes over time. The information above reflects currently available data and is not legal advice. Verify current status locally before traveling or obtaining zopiclone outside a prescription system.
Safety[edit]
- Acute toxicity
- Low
- Chronic toxicity
- Moderate
- Withdrawal
- Moderate
- Tolerance buildup
- slow
- Tolerance reset
- 10.5 days
- Physical
- Moderate
- Psychological
- Moderate
- Compulsive redosing
- Low
- Dose escalation
- Low
- Cross-tol.
- benzodiazepines · zolpidem · zaleplon
Toxicity
Acute toxicity
Deaths from zopiclone alone are rare.[7] Overdose with zopiclone as a single agent typically presents as deep sedation or coma, with respiratory depression uncommon in isolation. The benzodiazepine-site antagonist flumazenil can reverse zopiclone-induced sedation, consistent with the shared GABA-A mechanism.[7]
Fatality risk increases dramatically with polydrug overdose — particularly when zopiclone is combined with alcohol, opioids, or benzodiazepines.[7] Post-mortem forensic data include cases with zopiclone at therapeutic blood levels alongside lethal concentrations of other substances,[17] and cases with zopiclone at toxic concentrations (1,200 µg/L) in polydrug fatalities.[18]
European pharmacovigilance data identified over 9,200 zopiclone-associated adverse reactions across more than 6,200 patients, with zopiclone most frequently involved in overdose events among the three Z-drugs.[19]
Respiratory effects
At the standard 7.5 mg dose, zopiclone does not worsen breathing during sleep in published studies.[20][21] Data in patients with chronic lung disease or sleep apnea are limited.
Liver effects
No significant liver toxicity has been reported at therapeutic doses. A single case of acute liver injury was published for eszopiclone in a patient with pre-existing liver disease.[22] Because zopiclone is metabolized primarily by the liver, pre-existing liver impairment significantly increases drug exposure.[13]
Psychological risks
Zopiclone-associated neuropsychiatric effects include anterograde amnesia (memory gaps for events after dosing), complex sleep behaviors (sleepwalking, sleep-driving, sleep-eating), visual hallucinations, and behavioral disinhibition.[7][23]
Complex sleep behaviors are a distinct safety concern: individuals may drive, cook, or eat during partial arousal with no memory afterward.[24] Risk is elevated with concurrent sedating medications and pre-existing sleep disorders.[25]
Irritability, emotional lability, and paradoxical agitation have been reported, with higher incidence in elderly patients.[7][26] Epidemiological data associate long-term hypnotic use with increased depression and mortality risk, though whether this relationship is causal remains unestablished.[27]
Tolerance and dependence
Tolerance to zopiclone's sleep-promoting effects develops more slowly than for benzodiazepines. A 17-week sleep laboratory study showed sustained efficacy without measurable tolerance,[28] and eszopiclone data extend to 12 months.[3] Cross-tolerance with benzodiazepines is expected and confirmed, given the shared binding site.[2][11]
Physical and psychological dependence develop with prolonged use. Surveillance data indicate zopiclone's dependence risk is equivalent to zolpidem,[19] and abuse has been documented in addiction treatment populations.[29][30] Dependence potential is consistently characterized as lower than that of benzodiazepines but clinically significant, particularly in people with a history of substance use disorder.[2][15]
Discontinuation after chronic use produces rebound effect insomnia and withdrawal symptoms including anxiety, disturbed dreams, and nausea.[3] Unlike cognitive behavioral therapy for insomnia, zopiclone's benefits do not persist after stopping — rebound symptoms emerge upon cessation.[31] Gradual dose tapering is recommended.[32]
Drug Interactions
Zopiclone is metabolized by the liver enzyme CYP3A4, creating predictable interactions with drugs that inhibit or induce this enzyme.
CYP3A4 inhibitors increase zopiclone levels and intensify sedation. Erythromycin,[10][14][15] azole antifungals (ketoconazole, itraconazole), clarithromycin, nefazodone, ritonavir, and cimetidine all inhibit zopiclone metabolism and may require dose reduction.[33][15] Grapefruit juice may have a similar effect.[33]
CYP3A4 inducers reduce zopiclone levels and effectiveness. Rifampicin significantly accelerates metabolism,[15] and carbamazepine produces a similar effect.[10][14]
The alcohol interaction is additive at the level of brain effects rather than metabolism: alcohol does not substantially change how zopiclone is processed, but combined sedation is clearly dangerous.[34][15] Other CNS depressants — opioids, benzodiazepines, sedating antihistamines, and sedating antidepressants — carry the same additive risk.[33][15][7]
Polydrug overdose involving zopiclone and other CNS depressants is the principal context for fatality.[7]
Contraindications
9 knownConcurrent CNS depressant use is the most critical contraindication. Additive sedation and respiratory depression with alcohol,[34][15] opioids, benzodiazepines, and other sedating agents substantially increases overdose risk.
Breastfeeding is contraindicated due to zopiclone's excretion in breast milk at concentrations approaching those in blood.[9]
Severe liver impairment requires mandatory dose reduction to 3.5 mg, as bioavailability rises to approximately 97% and the half-life extends to approximately 8.4 hours.[13]
Elderly patients (over 70) require dose reduction to 3.75 mg due to substantially altered drug processing — bioavailability increases up to approximately 168% and half-life extends to approximately 8.1 hours — combined with elevated falls risk and cognitive vulnerability.[13][35][36]
History of substance use disorder confers elevated dependence risk.[19][30]
Breathing difficulties warrant caution given the GABA-A modulator mechanism, though zopiclone-specific data in chronic lung disease populations are limited.safety citation needed
Driving and machinery should be avoided for at least 8–10 hours after a 7.5 mg dose, given documented residual impairment persisting up to 10 hours.[6][7]
Pregnancy safety has not been established. Given the breast milk excretion data, fetal exposure is presumed.safety citation needed
Harm Reduction[edit]
Forms & Identification
Zopiclone circulates almost exclusively as commercially manufactured pharmaceutical tablets, making identification more straightforward than for substances sold as powders or liquids. Counterfeit tablets do exist, particularly in jurisdictions where zopiclone is not locally manufactured — visual inspection for consistent imprinting, correct tablet shape, and appropriate packaging provides a baseline check. Because the compound produces a distinctive bitter-metallic taste within minutes of ingestion, absence of this taste from a purported zopiclone tablet is a meaningful warning sign.
Guidelines
- Take zopiclone only when able to commit to a full night of sleep (7–8 hours minimum)
- Take the tablet immediately before getting into bed — not hours beforehand
- Do not exceed the prescribed dose (7.5 mg standard adult; 3.75 mg for elderly or liver-impaired patients)
- Do not crush, split, or dissolve tablets
- Avoid alcohol entirely on days zopiclone is taken
- Keep car keys out of reach before dosing if complex sleep behaviors are a concern
- Limit use to the shortest effective duration — daily use beyond 2–4 weeks increases dependence risk
- Do not stop abruptly after more than a few weeks of daily use — taper gradually under medical guidance
Set & Setting
Zopiclone is designed to induce sleep and should be taken only in a safe sleeping environment with no need to drive, operate machinery, or make important decisions for at least 10 hours. The bedroom should be prepared for sleep before dosing — once the drug takes effect, coordination and judgment deteriorate rapidly. Individuals with a history of sleepwalking or complex sleep behaviors should inform a household member that they have taken the medication.
Aftercare & integration. Next-day effects are common and expected. Residual cognitive impairment, slowed reaction time, and a persistent bitter taste may last up to 10 hours after a 7.5 mg dose. Do not drive or operate machinery during this period. Hydration and a normal meal help clear the lingering taste and support recovery.
If complex sleep behaviors occurred (evidence of eating, walking, or other activity with no memory), document what happened and consult a prescriber. This is a recognized adverse effect and may warrant discontinuation or dose adjustment.
Recovery & Support
Zopiclone dependence develops insidiously with regular use. The earliest sign is often difficulty sleeping without the medication — this rebound effect insomnia can feel like the original problem returning, making it harder to recognize as a withdrawal effect. If daily use has extended beyond a few weeks, do not stop abruptly: a gradual taper under medical supervision reduces withdrawal severity.
Cognitive behavioral therapy for insomnia (CBT-I) is the gold-standard alternative, with benefits that persist after treatment ends — unlike zopiclone, whose effects cease when the drug is stopped. Individuals struggling with zopiclone dependence can seek support through a prescribing physician, addiction services, or peer support organizations.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: Shallow or stopped breathing, blue-tinged lips or fingertips, inability to be roused by loud voice or sternal rub, or seizure activity all require immediate emergency response. Deep sleep alone is expected — unresponsiveness combined with abnormal breathing is the critical distinction.
- 1. Call emergency services immediately if breathing is slow, irregular, or absent
- 2. Place the person in the recovery position (on their side, airway clear) if they are unconscious but breathing
- 3. Do not induce vomiting
- 4. Do not leave the person alone
- 5. Monitor breathing continuously until help arrives
What to tell the dispatcher: Name the substance (zopiclone), approximate amount taken, time of ingestion, any other substances involved (especially alcohol, opioids, or benzodiazepines), and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
Reversal agent: Flumazenil can reverse zopiclone-induced sedation in a medical setting. It is not available over the counter and is administered only by medical professionals.
Legal Status[edit]
Zopiclone is a controlled substance in all major jurisdictions, classified alongside benzodiazepines and other sedative-hypnotics. Racemic zopiclone is not marketed in the United States, where only the isolated S-enantiomer (eszopiclone) is commercially available.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Schedule IV (Controlled Substances Act) | Final rule effective April 4, 2005.[4] Not commercially marketed; only eszopiclone (Lunesta) available. |
| United Kingdom | Schedule 4, Part I (Misuse of Drugs Act 1971) | Prescription-only medicine. Marketed as Zimovane. |
| Canada | Schedule IV (CDSA) | Available by prescription; generics widely available. |
| Australia | Schedule 4 (prescription only) | Distributed by Sanofi-Aventis as Imovane.citation needed |
| New Zealand | Class C5 (Misuse of Drugs Act) | Reclassified from prescription-only to controlled drug in 2022.citation needed |
| European Union | Prescription only (national regulations vary) | Widely available across EU member states. |
Frequently asked questions
What is Zopiclone?
Zopiclone is a cyclopyrrolone hypnotic and GABA-A receptor positive allosteric modulator used for short-term insomnia management. First approved in France in 1986, its active S-enantiomer is marketed separately as eszopiclone.
How long does Zopiclone last?
Total duration by route of administration — Oral: 3.5 – 9 hours. Ranges vary with dose and individual factors; see the duration table for onset, peak, and after-effect phases.
Where can I find dosage information for Zopiclone?
Psychedex publishes a dosage table for Zopiclone on this page covering these routes of administration: oral. Dose values are presented only in that table, always alongside their route of administration.
What are dangerous combinations with Zopiclone?
The highest-severity documented interactions for Zopiclone: Opioids (Lethal), Alpha-2 adrenergic receptor antagonist (Dangerous), Antipsychotics (Dangerous), Atypical antipsychotics (Dangerous), Benzodiazepines (Dangerous). See the interactions section for the full list with mechanisms and severity levels.
Is Zopiclone addictive?
Psychedex records tolerance and dependence data rather than a yes/no rating. Recorded tolerance indicators for Zopiclone: tolerance builds slow; full reset takes 10.5 days; cross-tolerance develops with benzodiazepines, zolpidem, zaleplon. See the article's dependence and safety sections for recorded dependence data.
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First-person accounts of subjective effects, timing, and outcomes — submitted for harm reduction.
references
- [1]
- [2] ^abcdMonti JM, Pandi-Perumal SR (2007) Eszopiclone: its use in the treatment of insomnia — Neuropsychiatric Disease and Treatment PMID:19300573
- [3] ^abCaille G, du Souich P, Spenard J, Lacasse Y, Vezina M (1984) Pharmacokinetic and clinical parameters of zopiclone and trimipramine when administered simultaneously to volunteers — Biopharmaceutics & Drug Disposition PMID:6743780
- [4] ^abcPatat A, Paty I, Hindmarch I (2001) Pharmacodynamic profile of Zaleplon, a new non-benzodiazepine hypnotic agent — Human Psychopharmacology PMID:12404558
- [5]
- [6] ^Gaillot J, Heusse D, Hougton GW, Marc Aurele J, Dreyfus JF (1982) Pharmacokinetics and metabolism of zopiclone — International Pharmacopsychiatry PMID:7188377
references
- [1] ^abcFleck MW (2002) Molecular actions of (S)-desmethylzopiclone (SEP-174559), an anxiolytic metabolite of zopiclone — Journal of Pharmacology and Experimental Therapeutics PMID:12130723
- [2]
- [3] ^abcdMonti JM, Pandi-Perumal SR (2007) Eszopiclone: its use in the treatment of insomnia — Neuropsychiatric Disease and Treatment PMID:19300573
- [4] ^abcDEA (2005) Schedules of controlled substances: placement of Zopiclone into Schedule IV. Final rule — Federal Register PMID:15806735
- [5] ^abCaille G, du Souich P, Spenard J, Lacasse Y, Vezina M (1984) Pharmacokinetic and clinical parameters of zopiclone and trimipramine when administered simultaneously to volunteers — Biopharmaceutics & Drug Disposition PMID:6743780
- [6] ^abcPatat A, Paty I, Hindmarch I (2001) Pharmacodynamic profile of Zaleplon, a new non-benzodiazepine hypnotic agent — Human Psychopharmacology PMID:12404558